Conventionally, a power consumer has witnessed the widespread use of a distributed power source apparatus.
In recent years, there are an increasing number of cases where a plurality of power source apparatuses are jointly used. For example, when a storage battery is introduced to a consumer in which a fuel cell is provided, it is possible to cover an insufficient amount of power supplied from the fuel cell to a load device by using the storage battery (for example, see Patent Literature 1).
Further, a reverse power flow, to a grid power source, of output power from a power source apparatus, such as a fuel cell and a storage battery may be prohibited. In this case, it is general that a current sensor for preventing a reverse power flow is provided on a grid power source line, and on the basis of the output from the power sensor, the output from the power source apparatus is controlled so that a reverse power flow is not generated.